The term "bow" is used herein to mean a "mechanical accelerating device for projectiles," covering hand bows for accelerating arrows as well as crossbows for accelerating arrows, bolts or balls as well as all other devices in which a projectile is accelerated with the aid of bows. Subdividing the projectiles by their length and their weight distribution into arrows, bolts and balls is of no importance for the present invention. Accordingly, in the following the term "arrow" or "arrows" which is often used alone includes all other projectiles.
Crossbows have long been known to the art--the traditional design dates back to the 14.sup.th century or earlier, when very high powered crossbows were effective even against armored horsemen. Modern crossbows now use sighting mechanisms of various sorts, but otherwise are little changed except in style and constructional materials. Draw weights are dramatically lower. A large medieval crossbow of circa 1500 AD might have a draw weight of 1200 lbs and a range of 450 yards. These days crossbows rarely exceed 150 lbs draw weight. The basic elements are a short, horizontally mounted bow, a trigger mechanism (latch) to hold back the string, and the arrow (called `bolt` or `quarrel`) which sits in a groove. Crossbows normally use rifle style stocks; indeed, the modern rifle design originated with the medieval crossbow. Sights may be aperture sights as found on a rifle, pin sights as on a compound handbow, or telescopic sights. A modern 165 1b draw weight heavyweight crossbow will achieve similar projectile speeds to a 60 lb peak draw weight compound hand bow, and the bolt and arrow weights are also similar (30 gms).
The bow, being relatively short compared to a vertical bow, will require comparatively more force to bend the bow. Indeed, most crossbows must be cocked by using the feet and legs, or mechanical levers or screws in older times for very powerful bows. Because of the large amount of force applied, there are safety concerns created by the structure of a conventional crossbow. The bowstring, being external, sweeps along the top of the bow. A crossbow shooter who sticks a thumb too high will risk injury from the moving string. The bow limbs themselves stick out to the sides of the bow, and pose additional safety concerns. If they hit a tree trunk or similar immovable object, there is a large potential for damage to the archer and the crossbow as the limb suddenly stops and accelerates the buttstock sideways.
In addition, the use of the bow and string introduce elements of inaccuracy, unless the arrow is exactly centered on the string, and the crossbow is cocked consistently in the same place, and as close to center as possible. Cocking the bow even 1/16" off center will drastically change the crossbow's point of impact.